Automatically generate documentation

[HackerFoo]

Context from https://github.com/SymbiFlow/fasm/pull/28:

Are the docs from the Python code and C++ code getting included into the sphinx output?

@mithro I ran make html in docs/, but I don't see anything related to the source code. Sounds like it was never set up for this repository (hence it might be okay to bump this to a github issue to follow up on). Please reach out to @rw1nkler, he did this for Verilog To Routing - https://docs.verilogtorouting.org/en/latest/api/vpr/contexts/